The present invention is in general directed to an improvement of a magnetic and reproducing apparatus of the type utilizing open-reel or cassette magnetic tape, and more particularly to a magnetic recording and reproducing apparatus having the function of preventing unstable operation due to the slack of the magnetic tape between the supply reel and the take-up reel.
For the better understanding of the present invention, some disadvantageous phenomena encountered in the tape recording and reproducing apparatus of the prior art due to slack the magnetic tape will first be studied briefly with reference to FIG. 4 in which some examples of malfunction due to tape slack in a tape recording and reproducing apparatus of dual capstan type are illustrated.
FIG. 4A shows an example in which slack exists in the tape portion of supply reel side. In this case, tape tension in the magnetic head 30 side, being bounded by the capstan 4, becomes larger than that of supply reel 2 side, which causes some portion of the magnetic tape 36 to be protruded out of the capstan 4 and pinch roller 34, resulting in twisting or cutting of the tape 36 as well as deterioration of wow-flutter characteristic.
FIG. 4B shows an example in which slack of the tape 36 exists between the capstan 4 and another capstan 4. In this case, tape transferring at constant speed may not be obtained, and noises and signal drop-out due to unstable contact between the tape 36 and the magnetic head 30 will be encountered.
FIG. 4C shows an example in which slack of the tape 36 exists in take-up reel 3 side. In this case, since the take-up reel cannot absorb all of slack, the remained slack portion of the tape 36 may occasionally happen to twist around another member of the recording and reproducing apparatus.
Although those examples have been described about the magnetic recording and reproducing apparatus of the type of dual capstan, these disadvantageous phenomena may also be encountered in a recording and reproducing apparatus of the type of single capstan. As described above, slack of magnetic tape existing before the tape is started to play may deteriorate the performance of such magnetic recording and reproducing apparatus.
In order to avoid such disadvantage as described above in connection with the example shown in FIG. 4A, the prior art has attempted to increase the accuracy of parallelism between capstan and pinch roller. This and other attempts, however, have not been successful as a practical matter.
Accordingly, it is an important object of the present invention to provide an improved magnetic recording and reproducing apparatus in which slack of tape can be eliminated for stable performance in advance before magnetic head contacts the tape and the tape is started to play.